Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/78—Preparation processes
  • C08G63/82—Preparation processes characterised by the catalyst used
  • C08G63/85—Germanium, tin, lead, arsenic, antimony, bismuth, titanium, zirconium, hafnium, vanadium, niobium, tantalum, or compounds thereof
  • C08G63/86—Germanium, antimony, or compounds thereof
  • C08G63/866—Antimony or compounds thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst

Definitions

• This invention relates to a method for preparing finely and evenly divided elemental antimonium which has the physical and general characteristics required for a catalyst to be used in the preparation of linear polyesters.
• the starting materials are dimethylterephthalate, or the terephthalic acid as such, and, among the diols, ethylene glycol is the most commonly adopted one.
• the first stage of the method is an ester interchange of the two reactants, which is generally called a reesterification reaction.
• this first stage gives bis-(2-hydroxyethyl) terephthalate, which is the monomer to be polymerized in the subsequent stage in order to convert it into the end product, that is, the linear polyester.
• Said reesterification reaction is usually carried out in the presence of a catalyst in order that the reaction in question be accelerated, and the catalysts which are most used to this purpose are, for example, the organic salts of zinc, manganese or salts of other metals.
• the product obtained from said ester interchange is subsequently polymerized or polycondensed until a linear polyester having a high molecular weight is obtained, which is adapted to be converted into important commercial products, more particularly fibers or yarns.
• the monomer is obtained in the first stage and should then be polycondensed to originate the desired end polymer, and it is known that, in both these stages, catalysts are conventionally used to accelerate the process run, such as compounds of bivalent or trivalent metals, for example salts of calcium, zinc and others.
• a granular catalyst must have such a size as to become finely dispersed within the reaction mass and more particularly, in the present case, in the mass of the monomer, for example bis-(2hydroxyethyl) terephthalate to be condensed.
• these methods require chemical and physical means which hardly ensure a satisfactory reproducibility of the results. ln addition, these methods could be conducive to catalysts incapable of affording to the polymer the desirable whiteness rating.
• the most commonly used are the chemical reduction of antimony com pounds and the grinding of powders, while more interesting and difficult methods are available, such as the electric reduction to powder of a metal dispersed within a liquid, the thermal decomposition of antimony compounds, the grinding of elemental antimony with the aid of airjets and others.
• Powdered elemental antimony of commercial grade is formed by particles having a size which is generally over 10 microns, whose average value is between 10 and 1000 microns.
• the elemental antimony which can be obtained by reduction chemical reactions is formed by particles whose size varies according to the method and the conditions under which the reaction has been carried out, said particles consisting of aggregates of unit particles, having a rather coarse size, for example over microns (for example 250 microns), or unit particles having a lesser size, for example lO-lOO microns.
• a simple and quick method has been devised, which is based on physical treatments only, for the preparation of elemental antimony in fine particles, the latter exhibiting a predetermined and constant uniformity of grit size and being adapted to be used as a highly efficient catalyst in the production of polyesters, more particularly high-molecular-weight linear polyesters.
• Said physical treatments can be applied to elemental antimony in powder form as obtained from the market, or from conventional chemical reactions, since the elemental or the antimony resulting from conventional reactions is unacceptable as a catalyst in a polycondensation reaction.
• the inventive method is characterized in that powdered elemental antimony, formed by particles or particle-aggregates having substantially a diameter over l0 microns, is subjected to physical size-reducing treatments, homogenization and dispersion, such as to permit the obtention of an antimony dispersion formed by particles having substantially a size in the order of 10-20 microns, in a liquid which is compatible with the subsequent use as a catalyst, the elemental antimony thus obtained being a catalyst which has a high efficiency for the production of polyesters, more particularly linear polyesters having a high molecular weight.
• the powdered elemental antimony is dispersed within said liquid, usually ethylene glycol,
• Said final dispersion is adapted to be directly used as a catalyst in the production of polyesters. It can be introduced in the initial reesterification stage, or, as an alternative, it can be added to the reaction mass at the outset of the polycondensation stage aforementioned.
• the process involves direct esterification of the bicarboxylic acid and the diol, as outlined above, and the subsequent polycondensation stage
• said dispersion can be added to the reaction mass during the first stage or at the beginning of the second stage.
• the elemental antimony obtained according to the invention can be used as a catalyst in both the esterification and polycondensation stages; it exhibits, however, its best properties during progress of the polycondensation stage.
• the antimony prepared according to the invention be associated, in said first stage, with a conventional esterification catalyst, such as a zinc salt, a calcium salt and others.
• said preliminary dispersion in the liquid by a mechanical stirrer rotated at a high speed is effected on dispersions having a concentration of antimony of from 0.1 to 1 percent.
• the final stage in the preparation of the catalyst that is the treatment in the colloid mill, is preferably carried out as a single step at room temperature, although different temperature might also be used.
• a settling treatment could be carried out, during a time of from a few minutes, for example minutes, to 6 hours, followed by the drawing off of the supernatant clear layer which contains the finest particles.
• the utility of carrying out said settling step is a function of the manner in which the previous treatments have been performed: it can be successfully used whenever the previous treatments have been conducted in such a way as to produce a large number of particles having a diameter which is in the neighborhood of microns.
• the settling step can be dispensed with, conversely, when the dispersion obtained has particles whose size distribution is satisfactorily uniform and between 10 and 20 microns, which occurs in the majority ofinstances.
• the dispersion of antimony particles obtained according to the inventive method contains particles having an average size within a very narrow range of values, and, more exactly, from ID to 20 microns.
• the size of the particles is thus very uniform and the dispersion has a grey color and can be easily admixed with and incorporated in the reaction mass in the process for producing polyesters, and without lump formation.
• the dispersion obtained after the treatment in the colloid mill is subjected to at least two consecutive filtrations through porous diaphragms, the first of which has pores whose nominal size is from 15 to 40 microns, and the second one has pores with a nominal size of from 5 to 15 microns.
• the controls made by passing the dispersions through the two porous diaphragms are a confirmation of the results obtained on samples of said dispersion with microscopical examinations carried out according to the conventional techniques.
• the starting material for performing the method according to the invention consists of powdered antimony, whose particles have, as an average, a size considerably greater than microns, as frequently occurs with commercial grade antimony, it is wiser to carry out two preliminary dry-grinding and wet grinding treatments on said material, so as to reduce at least the major portion of said particles to a size of less than 20 microns, then effecting said preliminary dispersion in a liquid and the subsequent treatment in the colloid mill.
• the two preliminary treatments aforementioned are intended to reduce the comparatively great size of said particles to such a value that they can be readily processed by said preliminary dispersion and the colloid mill, to obtain the desired size.
• the starting material consists of powdered antimony, composed of aggregates of particles having a size in excess of 100 microns, or of particles with a diameter between 10 and 100 microns, as is the case when antimony is the result of chemical reduction operations, then said preliminary treatments are redundant, inasmuch as the particles can be reduced to the desired size without any appreciable difficulty.
• the first of said preliminary treatments consists in one or more dry-grinding operations to give particles having an average diameter of less than 35 microns.
• dry-grinding operations are preferably carried out by treating the powdered antimony in a ball mill rotated at high speed, and causing the thusly ground product to pass through screens having 16,000- mesh gauzes, so as to permit that particles having a diameter substantially below 35 micron be detected.
• the resulting product is then subjected to the second preliminary treatment which comprises one or more grinding operations within a liquid, preferably ethylene glycol, to give particles having an average diameter of less than 20 microns.
• the second preliminary treatment comprises one or more grinding operations within a liquid, preferably ethylene glycol, to give particles having an average diameter of less than 20 microns.
• the wet-grinding operation is carried out by dispersing the antimony powder as obtained from the first treatment, in ethylene glycol at a concentration of l0-50 percent by weight of antimony in the liquid, and grinding said dispersion with ball mills or sandmills.
• Said dimensions of the particles can be determined with the conventional analytical tests, for example, microscopical examinations of the relevant samples.
• the product obtained is properly dispersed (preliminary dispersion) and then subjected in the colloid mill to a dispersion and homogenization action which leads to the desired end product according to the invention.
• the dispersion of antimony as obtained according to the invention, has the necessary and most desirable properties for its use as a catalyst in the production of polyesters, and more particularly of linear polyesters.
• polymerization tests have been carried out, by adding the dispersion obtained according to this invention, to the reaction mass, both in reesterification and polycondensation processes and in those processes which are based on the direct esterification of terephthalic acid with a glycol.
• the polymer thus obtained also shows the satisfactory characteristic of thermal stability; it withstands temperatures of 280-290 C., during long periods of time without exhibiting any degradation or other alterations liable to impair the polymer itself.
• EXAMPLE 1 A dispersion of elemental antimony in monoethylene glycol in the form of a fine and uniform particles having a size between and 20 microns is prepared according to the following procedure:
• Another fraction of the final dispersion thus obtained shows particles having a size substantially of from 10 and microns.
• a portion of said dispersion is used to obtain a spinnable polyethylene terephthalate polymer, as follows:
• test-polymerization reactor having a capacity of liters and equipped with a stirrer and distillation columns is charged with the following materials:
• DMT dimethyl terephthalate
• GE monoethylene glycol
• GE bihydrated zinc acetate
• trielhylsulfate 1.33 parts dispersion of Sb (0. 1% in GE) containing 2.4 parts Sb
• reaction mass is gradually brought to 220 C., during 7 hours, and, during this time all the methanol formed in the ester interchange reaction of dimethyl terephthalate and ethylene glycol is distilled off virtually entirely from the reactor.
• a gradual vacuum is then applied to the reaction system so as to attain, during 2 hours, a value of 0.5 to 1 mms. of mercury, the temperature being raised from 220 C., to 280 C.
• Polycondensation is completed by maintaining the reaction mass under a vacuum of 0.5 mms. of mercury at 280 C., during 3 hours.
• the formed polymer is then extruded under nitrogen pressure in cold water.
• Said polymer converted into granular form, is colorless and is water transparent.
• [n] 0.673 (intrinsic viscosity, measured at 20 C., in a mixture of phenol and tetrachloroethane in the weight ratio of 60 to 40, the concentration of the solution being 0.58 gr. of polymer in I00 mls.
• Filaments or yarns obtained from said granules have a clear color and have no lumps or dark spots.
• EXAMPLE 2 A sample of elemental antimony, in the form of an impalpable powder, is obtained by reduction of an aqueous solution of SbC 1,, acidified with hydrogen chloride, with zinc powder.
• the antimony particles, or particle-aggregates, have a size substantially over 10 microns.
• the powdered Sb is then converted into a 0.1 percent dispersion in ethylene glycol according to the procedure indicated under b) of example 1 and is then subjected to a pass in a colloid mill of the Manton-caulin type.
• this dispersion is essentially formed by particles having a size between 10 and 20 microns.
• An amount of 2,400 parts of said dispersion, containing 2.4 parts of Sb, is subjected to a polycondensation test, by using an implementation and a charge according to the same operative conditions as in example 1.
• the filaments or yarns obtained by melt-spinning of the granules exhibit a satisfactory clear color and do not show any staining or other undesirable discoloration.
• EXAMPLE 3 A specially provided stainless-steel esterification reactor equipped with a stirrer and a rectification column, containing 200 parts of prepolymerized polyethylene terephthalate having a average degree of polymerization of 2 kept at a temperature of 245 C., is charge during 1 hour with a slurry consisting of:
• terephthalic acid 50 parts of monoethylene glycol 0.05 parts of Sb slurried in 25 parts ofGE, obtained as in ex. 2.
• the Esterification reaction is carried out under a pressure of 3.5 kgs./sq.cm., at a temperature of 245 C., the water formed during the reaction being continually withdrawn for 1 hour.
• the balance of the reaction water is removed from the reactor by venting the system from 3.5 kgs./sq. cm. down to atmospheric pressure, during an additional hour.
• the ester thus obtained is transferred to a polycondensation reaction wherein the temperature of the reaction mass is brought, during 2 hours, to 280 C. while gradually applying a vacuum, from 760 mms. of mercury to 1 mm. of mercury.
• the polycondensation reaction is carried out within 5 hours at 280 C. under vacuum of l mm./Hg.
• the polymer thus obtained is extruded under nitrogen pressure in water and converted into granular form.
• the product has the following specifications m.p. 263 C.
• EXAMPLE 4 A sample of commercial powdered antimony having a grit size of 60 mesh (mesh width 250 microns) and a purity of 99 percent, is ground in a rod mill rotated at 15,000 rpm. then screened through a screen having a 16,000 mesh gauze until a powder is obtained having a grit size of less than 35 microns.
• the fine powder thus obtained is admixed with ethylene glycol, up to a percentage of 33.3percent of the whole mixture, until obtaining a uniform slurry which is subjected to grinding in a ball mill during 100 hours under an inert gas blanket.
• the fine dispersion thus obtained which contains particles having a diameter substantially less than 20 microns, is diluted to the concentration of 0.1 percent in ethylene glycol by stirring in a turbine dispersing machine for 5 minutes under an inert gas blanket at room temperature, then it is made homogeneous by treatment in a colloid mill of the Manton-Gaulin type.
• a portion of the dispersion so prepared is employed for producing a polyethylene terephthalate polymer according to the following procedure:
• a polymerization reactor is charged with the following materials:
• dimethyl terephthalate monoethylene glycol zinc formate [,000 parts 250 parts 0.2 parts (equal to 0.025 mols per l mols of DMTI 0.l6fi parts 400 arts
• the ester interchange and polymerization reactions are carried out with the same procedure as in example 2 the exception being that the duration of the high vacuum (0.5 mm of mercury) at 280 C., is as long as 2 hours 30 mins.
• the polymer obtained in the form ofgranules exhibits, upon crystallization and drying up to a moisture contents of less than 0.01 percent, the following specifications:
• the dispersion thus obtained exhibits, when observed through a microscope, a very uneven grit size for the particles or particle aggregates, characterized by average dimensions between 10 and 80 microns.
• Said polymer contains many black lumps, a few of which have a size of a few hundreds of microns and thus they are clearly visible by the unaided eye.
• a method for the production of poly-methylene terphalates by reacting a reagent selected from the group consisting of bicarboxylic organic acids and dialkyl esters thereof with ethylene glycol liquid in the presence 0 a catalyst consisting of a dispersion in the liquid glycol of antimony having a substantially uniform particle size in the range of from ID to 20 microns 2.
• a method for the production of poly-methylene terphalates according to claim 1 wherein the reaction mass is maintained under a vacuum of 0.5 to l mms. of mercury and at a temperature of 220 C., to 280 C., during the reaction.
• a catalyst for use in the production of poly-methlene terphalates by reacting a compound selected from the group consisting of bicarboxylic organic acids and dialkyl ethers thereof with ethylene glycol consisting of a dispersion in the ethylene glycol of antimony particles, whose sizes are substantially uniform and are in the range offrom 10 to 20 microns.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Health & Medical Sciences (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Polyesters Or Polycarbonates (AREA)

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Cited By (3)

Citations (3)

• 1968
  • 1968-03-22 NL NL6804117A patent/NL6804117A/xx unknown
  • 1968-12-16 US US784248A patent/US3624043A/en not_active Expired - Lifetime
  • 1968-12-20 FR FR1599385D patent/FR1599385A/fr not_active Expired
  • 1968-12-20 DE DE19681816087 patent/DE1816087A1/de active Pending
  • 1968-12-23 BE BE725914D patent/BE725914A/xx unknown

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Non-Patent Citations (1)

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